Composition for preparing high-performance glass fiber by tank furnace production

ABSTRACT

A composition for preparing high-performance glass fiber by tank furnace production comprising in preferred percentage by weight: 57.5˜62.5% of SiO 2 , 14.5˜17.5% of Al 2 O 3 , 13.5˜17.5% of CaO, 6.5˜8.5% of MgO, 0.05˜0.6% of Li 2 O, 0.1˜2% of B 2 O 3 , 0.1˜2% of TiO 2 , 0.1˜2% of Na 2 O, 0.1˜1% of K 2 O and 0.1˜1% of Fe 2 O 3  and (CaO+MgO)/MgO&gt;3, with the content of at least one of the three components, A 2 O, B 2 O 3  and TlO 2  higher than 0.5%, with the composition yielding glass fiber having improved mechanical property, causing the melting and clarification of glass and forming performance of fiber close to those of boron-free E glass, and facilitating industrial mass production by tank furnace processes with manufacturing costs close to those of conventional E glass.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Chinese Application201010176217.X, filed May 19, 2010 and International ApplicationPCT/CN2011/074283, filed May 18, 2011, both of which are incorporated byreference herein.

FIELD OF INVENTION

The invention relates generally to compositions for preparing glassfiber, in particular to compositions for preparing high-performanceglass fiber by tank furnace production methods.

BACKGROUND

Glass fiber is an inorganic fiber material that is useful to reinforceorganic polymer materials that in turn are used to preparehigh-performance composites or to reinforce inorganic materials, such ascement, for road construction. The production of glass fiber, a specialglass, has been difficult. Therefore, the usage amount of glass fiber isrestrained due to its relatively high production cost. The introductionof the tank furnace in 2000 has caused a breakthrough in the art of massproduction of glass fiber, by significantly reducing the cost of massproduction of glass fiber, thus expanding the fields of application forand usage amounts of glass fiber since then. However, limitations due tothe heating method and refractory material associated with tankfurnaces, production of glass fiber by tank furnace methods ofproduction require that the high temperature viscosity of the glasscomposition is limited, that is, it should not be too high. Generally,the forming temperature of a glass composition should be less than 1300°C., and at least 50° C. higher than its liquidus temperature.

The standard glass composition for preparing continuous glass fiber,commonly known as “E” glass, includes the following components inpercentage by weight as per the ASTM D578-00 Standard: 0-10% of B₂O₃,16-25% of CaO, 12-16% of Al₂O₃, 52-62% of SiO₂, 0-5% of MgO, 0-2% ofalkali oxide, 0-1.5% of TiO₂, 0.05-0.8% of Fe₂0₃ and 0-1% of F₂.Melting, clarification and fiber drawing can be done to E glass at lowtemperature. The forming temperature is generally lower than 1280° C.,which meets the requirements of mass production by tank furnace.Production of E glass began approximately in 1940. However, E glassremains the composition of over 90% of glass fiber produced around theworld.

In the 21^(st) century, as science and technology develops, improvementof the performance of fiber-reinforced composites is required, therebyrequiring glass fiber having better performance characteristics thanprior glass fiber. Ordinary E glass fiber, which contains about 7% ofB₂O₃ in percentage by weight, has been unable to meet the performancedemands in certain fields of use, including, for example manufacturingof wind turbine blades, high-performance GRP (Glass Reinforced Pipe(s))and automobile components due to its relatively poor mechanicalproperties, particularly its monofilament strength.

Boron-free E glass fiber is known, as described for example in U.S. Pat.No. 5,789,329 (“the '329 patent publication”), and improved E glassfiber is known, as described in U.S. Pat. No. 6,136,735 (“the '735patent publication”). While the boron-free E glass fiber and improved Eglass fiber described in those two patents have relatively bettermechanical performance than ordinary E glass fiber, neither meet thedemands required in such special fields of use as wind turbine bladesand high pressure pipes.

Compositions of high-performance glass fiber are known and described,for example, in U.S. Pat. No. 3,402,055 (“the '055 patent” or “the '055patent publication”), France Patent FR-A-1,435,073 (“the French '073patent publication”) and Chinese Patent Application CN94111349.3 (“theChinese '349 publication”). The main component of the high-performanceglass fiber described in each of these three patent publications isSiO₂—Al₂O₃—MgO or SiO₂—Al₂O₃—CaO—MgO, each of which is different fromSiO₂—Al₂O₃—CaO—B₂O₃, the main components or ingredients of E glassfiber. Although the glass fibers described in these three patentpublications have relatively great mechanical strength and high modulus,the requirements of mass production by tank furnace can not be fulfilledpresently.

To be specific, the molding or forming temperature of typical S-2 glassfiber, as described in the '055 patent, exceeds 1500° C., and themolding or forming temperature of R glass fiber, as described in theFrench '073 patent publication is about 1410° C. The temperatures formelting, clarification and wire drawing operations of these two glassfibers are extremely high and exceed the maximum temperatures that canbe reached during tank furnace production. The Chinese '349 patentpublication describes a high-performance #2 glass fiber whose forming ormolding temperature is about 1245° C., but it liquidus temperaturereaches 1320° C. Thus, for the Chinese '349 patent publication glassfiber, the ΔT (the difference between the forming temperature and theliquidus temperature) is −75° C. However, in general a positive ΔT valueexceeding 50° C. is required during tank furnace production. Therefore,the glass fibers described in these three patent publications are notsuitable for mass production by tank furnace production processes.

Due to the restrictions related to production mode or to failure toachieve mass production of high-performance glass fiber by tank furnacemethods of manufacturing, the manufacturing costs and ultimate prices ofhigh-performance glass fibers are extremely high, thereby seriouslyaffecting the total output relative to demand. As a consequence,high-performance glass fiber is typically used only in such fields asaviation, aerospace, national defense, military and the like. There is ahigh demand for high performance glass fiber in relatively newindustries and applications, such as blades for high-power windturbines, high pressure pipe lines and pressure vessels, for whichcurrent production levels of high-performance glass fiber can not meetthe demand.

SUMMARY

The compositions and processes described herein overcome the drawbacksof known compositions and processes for manufacturing high-performanceglass fiber by providing improved compositions and methods ofmanufacturing high-performance glass fiber.

In accordance with the above mentioned objectives and principles, apreferred composition for preparing high-performance glass fibercontains SiO₂, Al₂O₃, CaO, MgO, Li₂O, B₂O₃, TiO₂, Na₂O, K₂O and Fe₂O₃,the relative proportions of which are listed below by weight percentage:

SiO₂  57.5~62.5% Al₂O₃  14.5~17.5% CaO  13.5~17.5% MgO  6.5~8.5% (CaO +MgO)/MgO >3 Li₂O  0.05~0.6% B₂O₃ 0.1~2% TiO₂ 0.1~2% Na₂O 0.1~2% K₂O0.1~1% Fe₂O₃ 0.1~1%Also, the percentage content of at least one of the threecomponents—Li₂O, B₂O₃ and TiO₂ should be higher than 0.5%, and withinthe ranges listed above.

These and other embodiments, features, aspects, and advantages of theinvention will become better understood with regard to the followingdescription, appended claims and accompanying drawings.

DETAILED DESCRIPTION

Described herein are compositions and processes for preparinghigh-performance glass fiber that address the problems associated withknown high-performance glass fiber production methods. Thesecompositions and processes are based on maintaining high mechanicalproperties of the resulting glass fiber, and on causing the melting,clarification and forming performance of glass fiber to be close tothose of boron-free E glass. The presently described compositions andprocesses also facilitate industrial mass production by tank furnace andwith manufacturing costs close to that of conventional E glass.

As is well known by those skilled in the field glass fibermanufacturing, four basic parameters are typically used to specify thecharacteristics and describe advantages of specific glass fibercompositions:

1. Forming or Molding Temperature. The forming temperature is thetemperature when the viscosity of the molten glass is 10³ poise/h.

2. Liquidus Temperature. The liquidus temperature is the temperaturewhen the molten glass cools off and starts to form a crystal nucleus,i.e., the maximum temperature of glass devitrification.

3. ΔT value. ΔT value is the difference between the forming temperatureand liquidus temperature, indicating the possible temperature range forfiber drawing and formation.

4. Monofilament strength. Monofilament strength is the bearable drawingforce of monofilament fineness of glass fiber.

The above four basic parameters and measurement methods are well knownto those skilled in this field. As will be shown, the presentlydescribed glass fiber compositions have a much lower forming temperatureand liquidus temperature than conventional S glass. These lower formingtemperatures yield numerous advantages, such as meeting the requirementsfor tank furnace production processes; helping to lower energyconsumption; reducing the risk of corrosion of furnace fireproofingmaterials; and reducing aging of the furnace's crucible well duringoperation at high temperatures. Compared with traditional E glass, thepresent glass fibers have much higher monofilament strength. As aresult, the presently described compositions provide advantageousbalances among the founding and fiber drawing performance of the glassduring production, advantageous mechanical properties of the resultingglass fiber, and facilitate industrial mass production by tank furnaceproduction processes.

In accordance with the above mentioned objectives and principles, apreferred composition for preparing high-performance glass fibercontains SiO₂, Al₂O₃, CaO, MgO, Li₂O, B₂O₃, TiO₂, Na₂O, K₂O and Fe₂O₃,the relative proportions of which are listed below by weight percentage:

SiO₂  57.5~62.5% Al₂O₃  14.5~17.5% CaO  13.5~17.5% MgO  6.5~8.5% (CaO +MgO)/MgO >3 Li₂O  0.05~0.6% B₂O₃ 0.1~2% TiO₂ 0.1~2% Na₂O 0.1~2% K₂O0.1~1% Fe₂O₃ 0.1~1%Also, the percentage content of at least one of the threecomponents—Li₂O, B₂O₃ and TiO₂ should be higher than 0.5%, and withinthe ranges listed above.

SiO₂ is the main oxide for forming the base of glass and plays a role instabilizing other components. The mass percent of SiO₂ in a preferredembodiment ranges from 57.5˜62.5%. Excessively low content of SiO₂ leadsto lowered mechanical properties of the resulting glass and magnifiesthe glass's tendency towards devitrification. Also, too much SiO₂ willcause high viscosity, thus leading to difficulties in melting,clarification and subsequent fiber drawing of the resulting glass. Themost preferred SiO₂ content ranges from 58˜60.5%.

As an important glass network intermediate oxide, the preferred range ofAl₂O₃ content is 14.5-17.5%, and the most preferred range is 15.5-16.5%.In the presently described compositions and processes most of the Al₂O₃enters into the glass network in form of AlO₄, which combines with SiO₂,and plays an important role in determining the mechanical properties ofthe resulting glass and in preventing phase separation anddevitrification. Lowering the content of Al₂O₃ lowers the mechanicalproperties and raises the liquidus temperature to a point where if theAl₂O₃ content is too low, the mechanical properties of the resultingglass fiber will be lowered to an unacceptable point and the liquidustemperature will be too high. Specifically, if the content of Al₂O₃ istoo high, the network structure of the resulting glass will be broken bythe eight-coordinate [AlO₆] and raise the temperature of glassdevitrification.

In addition, the range of SiO₂+Al₂O₃ content in the preferredcompositions is strictly specified, that is, the range is 73-80% byweight, which will ensure excellent mechanical properties and facilitateindustrial mass production by tank furnace production processes.

CaO, as an important network modifying oxide, is especially effective inlowering the high-temperature viscosity of the glass. However, excessiveCaO content tends to cause devitrification, and can results inseparation of crystal from the glass, to form wollastonite. Thepreferred range of CaO content is 13.5-17.5%, and the most preferredrange is 14-16% by weight.

MgO and CaO have similar functions in glass, but the field intensity ofMg²⁺ is much higher than CaO and plays an important role in theimprovement of glass strength and modulus. However, the disadvantage ofMgO is that a high content of MgO will increase the tendency of theglass to devitrify, will increase the devitrification rate, and canresult in the separation of crystal from the glass, to form malacolite.The preferred range of MgO content is 6.5-8.5%, and the most preferredrange is 6.5-7.8% by weight.

The preferred sum of the CaO and MgO percentages by weight is20.5-23.5%, which results in lower liquidus temperature and lowerforming temperature, thus meeting the requirements for glass flow inlarge tank furnace production processes and ensuring the bestperformance of the resulting glass fibers.

Also, the preferred ratio of (CaO+MgO)/MgO is greater than 3. This ratiohas been found to improve the melting and clarification of the glass andto reduce the tendency towards devitrification of the glass. It isbelieved that this ratio functions to regulate and controldevitrification and to lower the liquidus temperature throughcompetition between Mg²⁺ and Ca²⁺ for anions. However, it is believedthat the different radius and field intensity of Ca ion and Mg ions willcause a mixed alkaline earth effect, with the preferred weightpercentages and preferred ratio of Ca and Mg content forming anaccumulation pattern that will tighten the glass structure andstrengthen the glass fiber. In addition, the preferred ranges of CaO andMgO will provide for a controllable devitrification rate, increasedglass flow, improved production capacity and more suitable massproduction by a tank furnace production method. The preferred ratio of2.01≦CaO/Mg0≦2.3 contributes to obtaining the best results in terms ofmodulus, strength, liquidus temperature and mold temperature, and themost preferred range of this ratio is 2.01-2.1, which produces the bestresult.

Because the addition of B₂O₃ may result in a noticeable fluxing action,the presence of B₂O₃ will help lower the glass viscosity, improve theglass-forming ability and improve devitrification performance. Becausehigh-performance glass is difficult to melt and form, adding a properamount of B₂O₃ proves quite effective in improving the performance ofglass melting and fiber drawing. However, the weight percentage of B₂O₃in a composition should be chosen so as to avoid the risk ofvolatilization and pollutant emission. The preferred range of B₂O₃content is 0.1-2% by weight, and the most preferred range is 0.6-1.5%.

It has been discovered that addition of TiO₂ will reduce thehigh-temperature viscosity of molten glass and accelerate melting.However, high content of TiO₂ will lead to an unfavorable yellow colorof the glass and to greatly increased cost of raw material. Thepreferred range of TiO2 content therefore is 0.1-2%.

It has also been discovered that addition of Na₂O and K₂O cansignificantly reduce the high-temperature viscosity of molten glass andcan accelerate melting and clarification of a glass batch. However, theweight percentage of Na₂O and K₂O should not be excessive, to avoidlowering the mechanical properties of the glass and lowering thechemical stability of the glass fiber. The preferred ranges of Na₂O andK₂O content are 0.1-2% and 0.1-1%, respectively.

It has been discovered that the addition of Li₂O will lower the glassforming temperature and strengthen the mechanical strength of the glassmore than addition of Na_(z) and K₂O. However, Li₂O will also increasethe liquidus temperature and the devitrification rate. Also, the rawmaterial price of Li₂O is relatively high so that its weight percentageshould be carefully controlled. The preferred range of Li₂O content is0.05-0.6% by weight.

The sum of the weight percentages of Na₂O, K₂O and Li₂O is preferablyless than 2%.

It has been found that excessive percentages of Li₂O will increase theliquidus temperature and the devitrification rate, but that a properamount of B₂O₃ will reduce the negative consequences caused by theaddition of Li₂O. Considering the effect of B₂O₃, Li₂O and Ti₂O onliquidus temperature, forming temperature and devitrification rate, thecontent of any one of them should be greater than 0.5% in order toprovide relatively easier drawing and founding, and to bettermonofilament strength.

Addition of Fe₂O₃ can improve devitrification of the glass, and improvethe strength and modulus of the glass fiber. However, because excessiveferric ion and ferrous ion will significantly tint the glass and lead todifficulty in glass melting, the weight percentage used should belimited. The preferred range of Fe₂O3 content is 0.1-1% by weight.

In addition to the compositions described above, the compositions formaking glass fiber can include a small amount of ZnO, 0.1-4% by weightwhich can, to some degree, reduce glass viscosity and improve itsdevitrification property and increase its chemical stability. However,excessive ZnO percentage will greatly increase the cost of raw materialof the glass. The preferred range of ZnO content is 0.1-2% by weight.

In accordance with the principles set forth above an alternatecomposition for preparing high-performance glass fiber contains SiO₂,Al₂O₃, CaO, MgO, Ll₂O, B₂O₃, TiO₂, Na₂O, K₂O and Fe₂O₃. of which theweight percentage ingredients are as follows:

SiO₂  58~60.5% Al₂O₃ 15.5~16.5% CaO 14~16% MgO 6.5~7.8% (CaO +MgO)/MgO >3 Li₂O 0.05~0.6%  B₄O₃ 0.6~1.5% TiO₂ 0.1~2%  Na₂O 0.1~2%  K₂O0.1~1%  Fe₂O₃ 0.1~1% 

Compared with prior art compositions, the presently describedcompositions for preparing high-performance glass fiber contain lowboron and regulate calcium oxide and magnesia content. The glass fibersmanufactured with these compositions not only have good mechanicalproperty but also share similarities with boron-free E glass in theproperties of melting, clarification and fiber formability. Thesecompositions are additionally advantageous because they facilitateindustrial mass production by tank furnace processes, and withmanufacturing costs close to that of conventional E glass.

Exemplary compositions and manufacturing processes within the scope andprinciples of the present inventions are described below. The presentmanufacturing processes provide glass samples or working glass made byhigh-temperature electric furnaces and with natural minerals used as rawmaterials. The natural minerals include, for example, pyrophillite,kaolin and quartz powder to generate SiO₂ and Al₂O₃; calcined dolomiteor dolomite to generate CaO and MgO; calcined limestone and limestone togenerate CaO; borocalcite to generate B₂O₃; and spodumene to generateLi₂O, etc. A batch of all the components is put into a platinum-rhodiumalloy crucible and made into glass samples or product byhigh-temperature electric furnace. The specific operating conditions ofthe process and properties of the produced glass, includingclarification and forming and liquidus temperatures of each glassformula are studied by comparing different melting time and temperaturesfor each batch.

Ten examples of production of high performance glass fiber will bedescribed. Each of the samples was prepared in a laboratory by producingglass fragments made in accordance with a composition as listed above.The ingredient mix for each example was placed into a single-hole,platinum-rhodium alloy crucible and heated for 2 hours at to about 100°C. higher than the glass forming temperature. The crucible temperaturewas then lowered to about 10˜20° C. higher than the glass formingtemperature. Next a fiber drawing test was conducted. In this process,the temperature of the crucible is strictly controlled, and the stateand temperature of fibers were observed in order to achieve the bestfiber drawing state. Then the remaining, untested glass monofilamentswere collected and tested for strength.

Ten examples of glass fiber made with the presently describedcompositions and by the above described process are listed in the Table1 and 2, as C1 to C10. There are two additional embodiments forcomparison: traditional E glass and traditional S glass. The content ofglass fiber compositions in the table are shown by weight percentage.

The tables also list each of the four basic parameters of (1) formingtemperature; (2) liquidus temperature; (3) ΔT value; and (4)monofilament strength.

The above four basic parameters and measurement methods are familiar totechnicians in this field. As shown in Tables 1 and 2, the glass fibercompositions of the present invention have a much lower formingtemperature and liquidus temperature than S glass. These lower formingtemperatures yield numerous advantages, such as meeting the requirementsneeded for tank furnace production; helping to lower energy consumption;reducing the risk of corrosion of furnace fireproofing materials; andreducing the aging of the crucible well at high temperatures. Comparedwith traditional E glass, the glass fibers of the present have muchhigher monofilament strength. As a result, the glass fibers of thepresent invention provide advantageous balances among the founding andfiber drawing performance of the glass and the mechanical properties ofthe glass fiber, and they facilitate industrial mass production by tankfurnace production processes.

TABLE 1 C1 C2 C3 C4 C5 C6 E glass S glass Ingredients SiO₂ 58.4 59.258.5 60.0 57.8 58.7 54.16 65 Al₂O₃ 16.1 15.7 15.3 15.8 16.0 16.0 14.3225 CaO 14.7 15.6 16.1 14.55 15.6 14.0 22.12 — MgO 7.3 6.8 7.5 7 7.4 6.750.41 10 B₂O₃ 1.1 1.0 0.9 0.5 0.8 1.2 7.26 — Na₂O 1.2 0.6 0.6 0.6 1.1 1.20.45 K₂O 0.22 0.22 0.22 0.24 0.22 0.24 0.25 — Li₂O 0.2 0.2 0.2 0.6 0.40.2 — — Fe₂O₃ 0.35 0.34 0.34 0.36 0.34 0.36 0.35 Trace amount TiO₂ 0.350.34 0.34 0.35 0.34 0.35 0.34 — F₂ — — — — — — 0.29 — ZnO — — — — — 1.0— — Parameters Forming 1268 1274 1278 1273 1266 1272 1175 1571temperature/° C. Liquidus 1204 1210 1215 1208 1208 1206 1075 1470temperature/° C. ΔT value/° C. 64 63 63 65 58 66 100 99 Monofilament4019 4086 4062 4106 3965 4056 3265 4380 strength/MPa

TABLE 2 C7 C8 C9 C10 E glass S glass Ingredients SiO₂ 57.5 61.0 58.659.0 54.16 65 Al₂O₃ 16.0 15.0 15.4 15.5 14.32 25 CaO 14.9 15.1 17.5 15.022.12 — MgO 7.3 6.8 6.5 7.0 0.41 10 B₂O₃ 2.0 0.5 0.5 0.5 7.26 — Na₂O0.43 0.4 0.4 0.4 0.45 — K₂O 0.22 0.22 0.22 0.22 0.25 — Li₂O 0.2 0.6 0.20.05 — — Fe₂O₃ 0.35 0.34 0.34 0.33 0.35 Trace amount TiO₂ 1.1 0.34 0.342.0 0.34 — F₂ — — — — 0.29 — ZnO — — — — — — Parameters Forming 12651276 1267 1266 1175 1571 temperature/° C. Liquidus 1200 1208 1205 12031075 1470 temperature/° C. ΔT value/° C. 65 68 62 63 100 99 Monofilament3960 4186 4010 4087 3265 4380 strength/MPa

Although specific embodiments of the invention have been described,various modifications, alterations, alternative constructions, andequivalents are also encompassed within the scope of the invention.

The specification and drawings are, accordingly, to be regarded in anillustrative rather than a restrictive sense. It will, however, beevident that additions, subtractions, deletions, and other modificationsand changes may be made thereunto without departing from the broaderspirit and scope of the invention as set forth in the claims.

What is claimed is:
 1. A composition for preparing high-performanceglass fiber comprising by weight percentages: SiO₂ 57.5~62.5% Al₂O₃14.5~17.5% CaO 13.5~17.5% MgO 6.5~8.5% (CaO + MgO)/MgO >3 Li₂O0.05~0.6%  B₂O₃ 0.1~2.0% TiO₂ 0.1~2%  Na₂O 0.1~2%  K₂O 0.1~1%  Fe₂O₃0.1~1% 

wherein the weight percentage of at least one of Li₂O, B₂O₃ or TiO₂ isgreater than 0.5% and wherein 2.01≦CaO/MgO≦2.3.
 2. A composition forpreparing high-performance glass fiber comprising by weight percentages:SiO₂  57.5~62.5% Al₂O₃  14.5~17.5% CaO  13.5~17.5% MgO  6.5~8.5% (CaO +MgO)/MgO >3 Li₂O  0.05~0.6% B₂O₃ 0.1~2.0% TiO₂ 0.1~2%  Na₂O 0.1~2%  K₂O0.1~1%  Fe₂O₃ 0.1~1% 

wherein the weight percentage of at least one of Li₂O, B₂O₃TiO₂ isgreater than 0.5% and wherein 2.01≦CaO/Mg≦2.1.
 3. A composition forpreparing high-performance glass comprising, by weight percentages: SiO₂ 57.5~62.5% Al₂O₃  14.5~17.5% CaO 14~16% MgO  6.5~7.5% (CaO +MgO)/MgO >3 Li₂O  0.05~0.6% B₂O₂ 0.1~2% TiO₂ 0.1~2% Na₂O 0.1~2% K₂O0.1~1% Fe₂O₃ 0.1~1%

wherein the weight percentage of CaO/MgO is 2.01-2.3.
 4. A compositionfor preparing high-performance glass comprising, by weight percentages:SiO₂ 57.5-62.5% Al₂O₃ 14.5-17.5% CaO 14-16% MgO 6.5-7.5% (CaO +MgO)/MgO >3 Li₂O 0.05-0.6%  B₂O₃ 0.1-2%   TiO₂ 0.1-2%   Na₂O 0.1-2%  K₂O 0.1-1%   Fe₂O₃ 0.1-1%  

wherein the weight percentage of CaO/MgO is 2.01-2.1.
 5. A compositionfor preparing high-performance glass fiber comprising by weightpercentages: SiO₂ 57.5-62.5% Al₂O₃ 14.5-17.5% CaO 13.5-17.5% MgO6.5-8.5% (CaO + MgO)/MgO >3 Li₂O 0.05-0.6%  B₂O₃ 0.1-2.0% TiO₂ 0.1-2%  Na₂O 0.1-2%   K₂O 0.1-1%  

further comprising ZnO, in an amount of 0.1-4% by weight; wherein theweight percentage of at least one of Li₂O, B₂O₃TiO₂ is greater than 0.5%and, wherein 2.01≦CaO/MgO≦2.3.
 6. A composition for preparinghigh-performance glass fiber comprising by weight; percentages: SiO₂57.5-62.5% Al₂O₃ 14.5-17.5% CaO 13.5-17.5% MgO 6.5-8.5% (CaO +MgO)/MgO >3 Li₂O 0.05-0.6%  B₂O₃ 0.1-2.0% TiO₂ 0.1-2%   Na₂O 0.1-2%  K₂O 0.1-1%  

further comprising ZnO, in an amount of 0.1-4% by weight; and, wherein2.01≦CaO/MgO≦2.1.